Petrol engines for automobile vehicles currently being developed emit large quantities of carbon dioxide (CO.sub.2) into the atmosphere, at a rate of approximately 170 g of CO.sub.2 per 100 km travelled, as well as other emissions.
To meet draft European anti-pollution standards that will come into force in 2005, automobile vehicle engines will have to operate in a way that reduces CO.sub.2 emission by approximately 25%, i.e. to approximately 120 g.
The quantity of CO.sub.2 emitted is directly proportional to the fuel consumption of the engine and the solutions adopted are therefore directed to reducing fuel consumption.
A first solution based on the concept of indirect sequential injection into an inlet manifold upstream of the inlet valves uses an impoverished air/petrol mixture. However, the results of this solution are limited in that a too poor mixture leads to incorrect engine operation.
A second solution, referred to as "direct-injection", consists in placing injectors directly in a combustion chamber of the engine. According to this concept, on the one hand, the injector is subject to downstream pressure variations associated with the Beau de Rochas cycle and, on the other hand, the petrol injected must be metered very accurately. To this end, a high-pressure injection pump associated with a pressure regulator is used to supply fuel at high pressure to the injectors.
The high-pressure injection pump is a mechanical pump driven by the engine of the automobile vehicle. The rotation speed of the pump therefore depends on the engine speed.
The pressure regulator is therefore unable to assure a stable pressure at the injectors at particularly low engine speeds, for example during starting, which is prejudicial to good combustion.
An object of the present invention is to remedy the drawbacks referred to above by providing a device producing a stable petrol pressure at the injectors in order to reduce the fuel consumption and the level of CO.sub.2 emission without degrading engine performance.
Another object of the invention is to reduce the residual petrol pressure in the injectors when the motor is stopped or if the electrical power supply to a vehicle engine control system is cut off.